Fuel filler assemblies are used in refueling automotive vehicles to allow fuel to be dispensed from a fuel dispensing nozzle into the fuel tank. Fuel filler assemblies include a filler tube through which fuel flows from the fuel dispensing nozzle to fill the fuel tank. A vent is provided to permit vapor in the tank to be displaced as fuel is supplied to the fuel tank.
Fuel dispensing nozzles normally include an automatic shutoff which is activated by a rapid build-up of pressure which is sensed at the dispensing end of the fuel dispensing nozzle. Fuel is normally dispensed at a rate of approximately 12 gallons per minute.
The problem of fuel expulsion, a rare occurrence wherein fuel is expelled from the fuel filler assembly, is more likely to occur when the level of fuel in the fuel tank is high and pressure is increased within the vapor dome formed between the top of the liquid level in the tank and the top of the tank. The pressure within the vapor dome may be increased by high ambient air temperatures or an increase in temperature of the vehicle as a result of extreme operating conditions. When the level of fuel in the tank is at or above the inboard end of the filler tube, removing the fuel filler cap may cause a sudden reduction in pressure at the outboard end of the filler tube, forcing fuel to be expelled upward and out through the filler tube.
The fuel filler assembly must cooperate with the fuel dispensing nozzle and its associated automatic fuel shutoff system. Automatic fuel shutoff systems of fuel dispensing nozzles include a sensor near the tip of the nozzle which senses any increase in pressure at the nozzle. When the fuel tank is filled, displaced vapor escapes from the tank through the vent tube. When the vent tube closes by operation of the float valve, a sudden increase in pressure occurs within the tank. This increase in pressure reduces the fuel flow rate within the filler tube causing fuel exiting the nozzle to flow backward around the nozzle sensor. The nozzle sensor then activates the dispenser shutoff and terminates flow of fuel through the nozzle.
To minimize the possibility of fuel expulsion, overfilling the fuel tank should be avoided. In addition, pressure build-up within the tank that would cause the level of fuel in the filler tube to rise should be avoided.
A problem with pressure equalization devices, including check valves, involves the need to calibrate check valves for effective operation at various pressure and temperature conditions. If a check valve is used to close the vent tube, as shown in U.S. Pat. No. 4,610,284 to Bartholomew, false triggering of the automatic shutoff will occur if the vent tube check valve is not properly calibrated.
Design simplicity is important in mass production of fuel filler assemblies. Dependability also is important to assure proper operation of the non-expulsive fuel filler assembly.
These and other problems are solved and advantages are realized by the present invention.